1. The long-term aim is to obtain complete serum and cerebrospinal fluid profiles of endogenous fragments of myelin basic protein (MBP-SFs) of normal sugjects and of MS patients at different stages of their disease, and to determine what combination of critical MBP peptides would best monitor the disease process. 2. Under the auspices of a companion grant, four overlapping synthetic peptides, representing redidues 60-84 of human myelin basic protein (MBP), are in the process of being synthesized by genetic engineering. The peptides are: G14 (60-69), G15 (65-74), G16 (70-79), and G17 (75-84). These are the first four of 35 peptides that will be supplied to the project to be used as probes in the immunochemical search. The immunochemistry of the peptides will be studied in junction with chemically synthesized peptide S24 (TTHYGSLPK), the bovine variant of G15 (TAHYGSLPK). Since rabbit anti-MBP antisera contain populations of antibodies cross-reactive with the defined determinant THYGSL (residues 66-71), they will be expected to react well with G15; thus, G15 will be used as the link to current studies with the chemically synthesized probes. 3. Immunochemical and immunobiological studies of the chemically synthesized MBP peptides S24 (65-74 of bovine MBP) and S49 (69-84 of bovine MBP with Gly-77 and His-78 deleted) will be continued. S24, a completely homologous sequence in non-primate MBP, is the encephalitogenic sequence for rabbits. S49, an analogue of rat and guinea pig MBP peptides, is encephilotogenic in Lewis rats. A marker B-cell determinant is being sought for S49 in the same way that a marker B-cell determinant for S24 has recently been found. 4. Specific antisera to the marker determinants of S24 and S49 will be used to search for the possible existence of specific MBP-SFs in the sera and CSFs of Lewis rats and rabbits; moreover, immunoglobulins from the antisera will be radioiodinated and tested for possible brain-localizing properties on the basis that encephalitogenic peptide sequences, unlike intact native MBP, may lie external to myelin membranes. In addition the specific anti-peptide antisera will be tested for their capacity to participate in MBP-specific antibody-dependent cell cytoxicity mechanisms in keeping with the Stoner-Brosnan model of antibody-dependent cell-demyelination.